25 February 2010

Rofin Laser Fine Tuned For TFT Production

When we look around our home, or car for that matter, it seems that almost every electronic device has an LCD display of some description, with screen sizes ranging from miniature to over 50 inches in the case of LCD televisions.

In the vast majority of cases, every pixel in the screen is active. The rows and columns of the pixel matrix are activated using transparent indium tin oxide (ITO) conductive paths. As part of the process in the production of TFT displays, a conductive connection must be established between the rows and columns of the matrix – an intentional short circuit, as it were. However, at a later stage in the production process, this step must be carefully undone. The power and precision of Rofin’s new PowerLine SL 8 IC laser makes it the ideal tool for this intricate task.

High speed with high accuracy
A TFT panel edge can sometimes be over a metre long and the connection groups are distributed over the whole length. Each group of conductive paths has to be cut accurately and absolutely reliably with a line width of just 35 μm +/- 5 μm. In addition to the high accuracy required for this application, leading screen manufacturers demand processing speeds in excess of 400mm / second. These requirements for accuracy and speed combined with the physical size of the larger components poses some interesting production challenges.

Galvo deflection heads are often used to position a laser beam across the working area, however with a processing field of this size the resultant spot diameter would be too large, meaning the narrow line widths required could not be guaranteed across the whole field. The solution therefore is to use fixed optics, with the laser and optics combination mounted to one motor driven axis and the panel moved in the other direction by a separate axis. To maintain the high processing speeds demanded by manufacturers the laser needs to be both powerful and compact.

Rofin’s new PowerLine SL 8 IC has been developed specifically for the fine cutting operations required on TFTs. The beam source has been optimised to meet strict requirements on beam quality and pulse to pulse stability at high frequencies. A temperature management system with independent thermal monitoring, stabilization of all relevant optical components and heat dissipation via a cooling plate ensures long-term stability and performance, which is necessary for reliable continuous operation.
The PowerLine SL 8 IC reliably cuts ITO conductive paths with the specified line width of 35 µm, and the power available from this new laser means that it is capable of achieving much higher speeds than the 400 mm / second demanded by the leading screen manufacturers.

Back to top